In a fabricating technology of a portable communication unit, such as a cellular phone or a personal handyphone system, researches for decreasing sizes and weights of parts including batteries, casings, antennas, and electronic circuits to the utmost limits and for reducing consumed electric power are actively developed in order to realize a compactness and lightweight of the portable communication unit. Referring to the antenna, an inverted F shaped antenna or a chip dielectric antenna is adopted in order to save a space for accommodation it. As shown in Japanese Patent Applications, Laid-Open, No. 9-321529, the internal antenna is electrically connected with the printed circuit board on which a display, a key unit, and the electronic circuits are mounted via a feeding system composed of two leaf springs (a feeding spring and a grounding spring) in the conventional portable communication unit.
However, in the feeding system using the leaf springs, since distances between the surface of the printed circuit board and the feeding points of the internal antenna are large, it becomes necessary to increase strokes of metal elements surving as the leaf springs. Accordingly, feeding terminals of the feeding system become large in order to secure sufficient spring-pressures, and areas of lands for soldering the metal elements of the feeding system to the printed circuit board become large. Moreover, the feeding system using the leaf springs is apt to interfere with peripheral structural elements, hence the efficiency of the antenna is apt to be lowered, and the characteristic of the antenna is apt to be fluctuated.
An internal antenna including a feeding system which improves the efficiency and the accuracy in the assembling process and stabilizes the characteristics of the internal antenna by simplifying its structure is disclosed in Japanese patent Applications, Laid-Open, No. 9-8526.
FIG. 1 shows the structure of the internal antenna 100 mentioned in the above.
The internal antenna 100 is provided with a chassis 102 which is formed above a diectical plate 101. Soldering patterns 103a, 103b, 103c are formed on the chassis 102, on which a matching circuit (not shown) is set and soldered to the soldering patterns 103a to 103c. The internal antenna 100 is fixed to the shield case (not shown) by soldering. The shield case is molded out of thermoplastic, and a whole outer surface thereof is plated with metal. The shield case is lightweight and shields electronic circuits (not shown) accommodated therein electromagnetically. Moreover, ribs (not shown) fitting conducting elements 105a to 105d which are formed on a grounding pattern 104 are provided for the top surface of the shield case. Moreover, a radiator 106 is formed on a top surface of the internal antenna 100.
Since a position of the internal antenna 100 relative to the shield case can be easily determined and the internal antenna 100 is connected with the shield case electrically and mechanically, the accuracy in the assembling process is heightened, and the characteristic of the internal antenna is stabilized. Moreover, since the grounding pattern 104 is electrically connected with the plated metal layer on the top surface of the shield case via the conductive elements 105a to 105d, and the plated metal layer serves as the grounding plane of the internal antenna 100, metal elements situated under a bottom surface of the dielectric plate 101 which are used in the conventional internal antenna become unnecessary, and the number of the structural elements can be reduced.
However, in the conventional portable communication unit, it is a premise that the internal antenna 100 is positioned on the top surface of the shield case. Moreover, since the grounding pattern 104 of the internal antenna 100 is soldered to the top surface of the shield case which is plated with metal, soldering technique becomes necessary in a fabrication process of the internal antenna 100. Furthermore, since it is necessary to combined the internal antenna with the shield case, the position on which the internal antenna is to be situated is limited.